Liquid purification



Patented Sept. 1, 1942 UNITED STATES PATENT OFFICE LIQUID PURIFICATIONOliver M. Urbain and William B. Stemen,

Columbus, Ohio, assignors to Charles H. Lewis,

Hamster, Ohio No Drawing. Application July 10, 1939,

- Serial No. 283,673

5 Claims.

This invention .relates to water softening and liquid purification. Morespecifically, it relates to materials and processes for the removal ofcations from liquids by a process of cation or ducing same.

into contact with aggressive waters, in general have a low capacitywhich necessitates frequent regeneration. 0n the other hand, thenumerous synthetic zeolites which have been prepared have a much greatercapacity for cation exchange but are far less durable and disintegraterather rapidly when employed with aggressive waters.

We have found that, through the use of the materials and processeshereinafter described, the disadvantages inherent with both natural andsynthetic zeolites of the prior art are overcome, and that cationexchange may be effected in highly aggressive waterswhile, at the sametime,

frequent regeneration of the exchange materials may be avoided.

It is an object of this invention to provide materials and processes foremcient cation exchange. It is a further object of this invention toprovide materials, and processes for the preparation of such materials,which possess high capacity for cation exchange and which are highlystable when used even in aggressive waters. A still further object ofthis invention is to provide a simple and economic process by whichstable high capacity cation exchange materials may be prepared. Anotherobject of this invention is the provision of efficient methods ofefi'ecting cation exchange with such materials, and effectingregeneration of such materials when exhausted.

Other objects will be apparent to those skilled in the art from thefollowing description of the processes and materials employed.

The materials which we have found are particularly stable and possesshigh exchange capacity are those prepared in the following manner.

Hard or semi-hard coals, such, for example, as

Pocahontas or Pittsburgh #8, and bituminous 55 coals, such, for example,as Hocking coal, serve as a basis for our novel materials. Generallyspeaking, the hard and semi-hard coals yield cation exchange materialshigher in capacity than those prepared from the bituminous coals.

The initial step in the preparation of our cation exchange materialscomprises mixing the selected coal, in dry granular form, with anhydrousferric chloride and heating such a mixture to a temperature ofapproximatel 300* C., with constant stirring, until reactions betweenthe components of the mixture is complete.

It is of primary importance that the components of the mixture beentirely free from moisture, and for this reason the coal must be dryand the ferric chloride must be anhydrous.

In its anhydrous form, ferric chloride melts at 282 C. and sublimes at315 C. The reaction between coal and ferric chloride is'effected whenthe ferric chloride i in molten form, and therefore, reaction betweenthe components of the mixture must be affected at temperatures withinthis range, 1. e., between 282 C. and 315 C.

-Although the proportions of coal andferric chloride contained withinthe mixture is not critical, we have found that the best cation exchangematerials are those prepared when approximately 100 parts by weight ofcoal is reacted with BOp'arts by weight of ferric chloride. 30 A smallerproportion of ferric chloride results in the production of a materialhaving lower capacity for cation exchange.

In'general, the coal is ground and graded to a size lying within therange of 8 to 20 "mesh. It is then mixed with the anhydrous ferricchloproximately 300 C. with'constant stirring and agitation. 1 h 1Reaction between the components of the mix- 4 ture is generally quiterapid and is'usually completed in less'than 30 minutes. Completion ofthe reaction is indicated by the fact that the reaction mixture becomesthoroughly dry due to the disappearance of the molten ferric chloride.

After reaction between the components of the mixture is completed, themass is cooled and water washed until the water washings aresubstantially colorless. The reaction mass is then treated with analkaline solution of relatively 50 low concentration for a-period offrom approximately 10 to 30 minutes. Alkalie's, such for ex-- ample assodium and potassium hydroxide may be used for this purpose, and theconcentration of the alkali solution may vary from 2 to 10%.

After treatment of the reaction mass with ride and heated to the propertemperature, apl alkali solutions, the mass is water washed to free itof alkali, and is then dried.

By such a process, there is prepared a base exchange material of highcapacity and of unusual stability. When sodium hydroxide is used as thetreating agent, the base exchange material contains sodiumcations,,while, when potassium hydroxide'is the alkali employed, theresultant cation exchange material contains exchangeable potassium ions.1

The chemical explanation of the reaction involved in the preparation ofour novel materials is believed to be as follows.

It is believed that'when coal is treated with molten anhydrous ferricchloride, the ferric iron is partially reduced to "the ferrous state.The chlorine liberated by this oxidation-reduction reaction is thenbelieved to react with the hydrogen of volatile hydrocarbons of the coalopening up the ring structures thereof. Since gaseous hydrogen chlorideis given off in copious quantities, it

ness of 20.31 grains per gallon through 40 grams of the preparedexchange material contained in a small filter unit. The hard well waterwas passed through the cation exchange materials in' approximately onehour. The eiiluent from the filtrate was carefully tested for totalhardness and there was found a residual hardness of 10.06

- grains per gallons, thus indicating a removalof is believed that theferrous iron goes-into the -exchange position in the coal, and thatsubsequent treatment of the mixture, with an alkali metal hydroxideresults in replacement of the ferrous cation bythe alkali metal cation,thus producing a cation exchange material replete with exchangeablealkali metal cations.

Stated otherwise, it is believed that the ferric chloride oxidizescertain portions of the constituents of the coal to active groupings forbase or cation exchange. As fast as the active groupings are formed itis thought they ares-stabilized in the active state by the ferric orferrous iron present,

thus preventing further oxidation to an inactive state. The ferricchloride probably acts as a' condensing agent to stabilize the coalconstituents. The vigorous oxidation-reduction reaction is believed toopen up the ring structures to yield groupings active in base or cationexchange.

Although we believe the foregoing to be a satisfactory explanation ofthe chemistry involved in the formation of our active cation exchangematerials, it is to be understood that this explanation is not to beconsidered as limiting the invention in any way whatsoever.

Illustrative of materials prepared in accordance with the teachings ofthis invention, the followgraded by means of sieves to obtain a fractionbetween8 and 20 mesh. One hundred parts by weight of this fraction wasthoroughly mixed 6!!- with 80 parts by weight of anhydrous ferricchloride andthe mixture heated to a temperature of 300 C. with constantstirring for a period of approximately 30 minutes. The mixture was 8.24grains per gallon.

In order to ascertain the capacity of the cation 0 An exchange materialhaving a'fcation ex- I change capacity of approximately 32,000 grainsper cubic foot is believed quite novel in view of.

the fact that the best exchange material now available is believed tohave a capacity of only approximately 12,000 grainsper cubic foot.

- Example I! 1 y the same procedure outlined in Example I, a cationexchange material was prepared from a grade of bituminous coal known asHocking coal. There was obtained a yield of approximately 50.6% based onthe quantity of coal and anhydrous ferric chloride employed.

The capacity of this cation exchange material was tested in the samemanner as that prepared in Example I, and this material wasfound toremove 4.79 grains per gallon of total hardness from a solutioncontaining 20.31 grains per gallon. When calculated to the conventionalbasis for measuring capacity, this material was found to .haveacapacityof 18.625 grains per cubic foot.

It will thus be seen 'that materials prepared from bituminous coals bythe method herein described possess a higher capacity for cation ex-.change than the materials presently available.

as far as now known, but such materials, are not as effective as arematerials prepared in a similar manner from hard coals such as that usedin Example I. 4

' Example II! An effort was made to-prepare an effective cation exchangematerial from lignite by the method herein described. There wasobtained. however, ayield of only 10.0% computed from the quantity oflignite and anhydrous ferric chloride employed.

The capacity of the exchange material prepared from 'lignite was testedin a manner similar to a 5% solution of sodium hydroxide,.after whichthe sodium hydroxide solution was permitted to drain from the mass andthe mass thoroughly washed free of alkali. After thoroughly drying, theresidual mixture was screened through a 20 mesh screen and the dryproduct retained on the screen utilized for cation exchange. There wasobtained a 50.0% yield of dry products based on the total weight of coaland anhydrous ferric chloride employed. a

The eillciency of the cation exchange material prepared in this mannerwas tested by. passing 1o 5 employed in water softening or liquidpurificathat prepared in Examples I and II. From a solution containing20.31 -grains per gallon of totalhardness, only 0.94 grains per gallonwas removed. Computed on the basis of grains per cubic foot, thecapacity of this exchange material prepared from lignite was'found to beonly 3,635 grains per cubic foot.

The base exchange materials thus prepared are compounds may be separatedand removed from the treated water or purified liquids.

Reaction of the cation exchange materials pregallons of hard we Waterhaving a -h pared in accordance with this invention with hardnessforming cations are given in the following equation. For purposes ofillustration, the exchange materials are represented by the formulaZNaz, but this is representative only and it is to be understood thatsuch materials may contain other exchangeable cations and any number ofexchangeable cations.

ZNa: 0801003)! Sodium calcium calcium sodium zeolite bicarbonate zeolitebicarbonate After the exchange material has become exhausted, it may beregenerated by treatment with a solution of an alkali or an alkali metalsalt. A preferred process of regeneration comprises treating theexhausted exchange material with a solution containing from 2 to of analkali or of an alkali metal salt, such for example as sodium hydroxideor sodium chloride. The regeneratin solution should then be washed fromthe exchange material preferably by a solution free of calcium andmagnesium ions. It has been found convenient to utilize, as the washsolution after regeneration, a quantity of water which has passed ZCa2NaHCOz through the filter when the filter was first placed inoperation. After the regenerated exchange material is again in use, aquantity of the first water passing therethrough should be reserved forwashing after the next regeneration.

Representative equations for the regeneration of exchange materialswhich have been used to remove calcium and magnesium from hard water,are given:

ZCa ZNaOh ZNB] C8(OH): Calcium Sodium sodium calcium zeolite hydroxidezeolite hydroxide ZMg 2NaCl o ZNa; MgCl:

Magnesium sodium sodium magnesium zeolite chloride zeolite chloride Thecations removed from the water treated will, of course, be found in theregenerated solution, and, if recovery is desired, they can be re-.moved by conventional methods, such as fractional distillation orfractional crystallization.

Materials prepared in accordance with this invention are, in general,completely regenerative. Illustrative of the capacity of a regeneratedmaterial, there is given the following example.

Example IV This represents an increase in exchange capacity followingregeneration which, it is believed, is

due to the purification of the exchange material by the solutionemployed in the regeneration step.

It is to be expressly understood that the foregoing description andexamples are merely illustrative and are not to be considered aslimiting the invention beyond the scope of the subjoined claims.

We claim:

1. A process of base exchange comprising contacting hard water with acarbonaceous alkali metal zeolite preparedby effecting anoxidationreduction reaction between dry granular coal and anhydrousferric chloride in the molten state, and thereafter treating theresulting product with a solution containing alkali metal cations.

2. A process of base exchange comprising contacting hard water with acarbonaceous alkali metal zeolite prepared from the oxidation-reductionreaction between dry granular hard coal and anhydrous ferric chloride ata temperature between 282 C. and 315 C., and treating the resultingproduct with a solution containing alkali metal cations.

3. A process of exchanging cations in hard water comprising contactingthe said'water with a product prepared by effecting anoxidationreduction reaction between dry hard coal graded from 8 to 20mesh and anhydrous ferric chloride, said reaction taking place at atemperature between 282 C. and 315 C., and thereafter treating theresulting reaction product with a solution containing alkali metalcations.

4. A process of base exchange comprisng contacting hard water with abase exchange material prepared by mixing approximately 100 parts byweight of coal graded to from 8 to 20 mesh, with approximately parts byweight of sublimed ferric chloride, heating the mixture to a temperaturebetween 282 C. and 315 C. in the absence of water to effect anoxidation-reduction reaction, with constant stirring until the moltenferric chloride disappears from the reaction mixture, cooling and waterwashing the resulting product, treating the resulting product with a 2to 10% solution of an alkali metal hydroxide, and thereafter washing anddrying the carbonaceous alkali metal zeolite thus obtained.

5. A process of exchanging cations in liquids comprising the steps ofbringing the liquid into contact with an alkali-treated product of anoxidation-reduction reaction between dry granular hard coal andanhydrous ferric chloride at a temperature between 282 C. and 315 0.,regenerating theexchange material when exhausted with a 2 to 10%solution of an alkali metal hydroxide free of cations which it isdesired to remove from the liquid, and .u. Sh contacting said materialwith additional liquids.

OLIVER M. URBAIN. WILLIAM R. STEMEN.

